It is proposed to continue our basic work on oxidative phosphorylation. Among the problems still to be solved are: The reconstitution of site 2 of oxidative phosphorylation and the complete resolution of the components required for the operation of the proton pump. The study of various pumps that contribute to the ATPase activity of the different tumor cells will be pursued. Particular emphasis will be placed on the mode of action of the Na ion K iDn ATPase of the plasma membrane and the Ca ions ATPase of sarcoplasmic reticulum. Attempts will also be made to elucidate the mechanism that governs the efficiency of these pumps.